THE HYDROUS PICE US. 



295 



not maintain itself horizontally at the surface of the water, but 

 it pokes out its head above water mark, and folds its antennae, 



THE METAMORPHOSIS OF Hydrophilus piccus. 



the club-shaped ends of which are partly hollowed out ; and thus 

 carries downwards a small bubble of air, which is pressed against 

 the sides of the thorax and of the abdomen, and which then comes 



